Seismicity in the Basin and Range province of Texas and northeastern Chihuahua, Mexico
— David B. Dumas

A four-year seismic study begun in January, 1976 has found the Basin and Range Province of West Texas and the adjacent areas of Mexico to be more seismically active than heretofore known. A five-station University of Texas seismic array covering the eastern and western sides of the Marfa Basin (table 1, fig. 1) has located or detected approximately 300 local and regional earthquakes (m_l <3.7) with a S-P time of less than 30 seconds. None of these local earthquakes has been located by U.S. Geological Survey instruments. Areas of detectable seismicity include the Van Horn area, the Marfa Basin (particularly the eastern side), and the Texas-Mexico border between latitude 30° and 31°N. The seismic pattern in the eastern side of the Marfa Basin forms a diffuse zone and is believed to represent an active fault, still unmapped. Seismicity along the eastern side of the Marfa Basin coincides with Muehlberger's (1978) proposed eastern boundary of Basin and Range faulting.

Hypocenter locations reported here were obtainnd by using the computer program HYPO 71 (Lee and Lahr, 1975) with P-wave arrival times and, whenever possible, S-wave arrivals. The crustal model used to locate these earthquakes  comprises three layers having velocities of 4.49, 6.18 and 6.75 km/sec, respectively, overlying a 8.37 km/sec half-space (Dumas, in preparation).